We provide cochlear implants (CIs) to young children who are deaf to alter their developmental course with regard to listening, speaking, learning, and socializing. The intended ultimate result in for the child to grow into a competent member of the hearing society. The brief history of developmental Cl research has shown that pediatric Cl users achieve substantial benefits in most of these areas. One set of studies proposed in this project aims to continue evaluating the outcomes of current and emerging practices of cochlear implantation. Our interests in current practices focus on whether the initial advantages of implantation early in life persist into the implant users'middle-school years. We will also focus on whether young adults implanted in childhood attain many of the social, occupational, and personal outcomes found among hearing individuals. Furthermore, we will examine whether some of these individuals identify with the Deaf community exclusively or with the hearing community as well. Within these studies, we will also examine the benefits of new practices in cochlear implantation. Specifically, we will examine whether bilateral implantation in infancy provides benefits to listening, speech, and language learning. Finally, we will evaluate if implantation before 12 months of age provides additional advantages to speech, language, and listening development compared to implantation after 12 months of age. A second set of studies shift away from outcome studies. These studies are concerned with advancing our understanding of the basic perceptual and cognitive systems that influence (and emerge) from a child's experiences with her Cl. The auditory experiences of the deaf child who receives a Cl appear to be superficially sufficient for the development of functional speech perception and spoken language. However, these children have qualitatively different auditory abilities and experiences that are likely to result in important differences in their development of speech perception. These children's abilities to perceive and employ properties of the speech signal subsequently bootstrap their language learning, and the development of memory systems involving phonological short-term and long-term memory that are important in language learning. A series of studies will examine how well infant Cl users develop preferences for properties of speech that have been shown to be salient to hearing infants. The manner in which phonemic categories are formed and subphonemic cues are used in perception will also be examined in these children. Finally, a model of the relationships between speech perception, short-term phonological memory, long-term phonological procedural memory, and declarative memory and early word learning will be examined in these children. These data will be later used to predict longer-term vocabulary development.